The present invention relates to a combustion engine and, more particularly, to an air and fuel supply system for use with an internal combustion engine.
An internal combustion engine may include one or more turbochargers for compressing a fluid, which is supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chambers. The fluid compressed by the compressor may be in the form of combustion air or an air/fuel mixture.
An internal combustion engine may also include a supercharger arranged in series with a turbocharger compressor of an engine. U.S. Pat. No. 6,273,076 (Beck et al., issued Aug. 14, 2001) discloses a supercharger having a turbine that drives a compressor to increase the pressure of air flowing to a turbocharger compressor of an engine. In some situations, the air charge temperature may be reduced below ambient air temperature by an early closing of the intake valve.
Early or late closing of the intake valve, referred to as the xe2x80x9cMiller Cycle,xe2x80x9d may reduce the effective compression ratio of the cylinder,.which in turn reduces compression temperature, while maintaining a high expansion ratio. Consequently, a Miller cycle engine may have improved thermal efficiency and reduced exhaust emissions of, for example, oxides of Nitrogen (NOx). Reduced NOx emissions are desirable. In a conventional Miller cycle engine, the timing of the intake valve close is typically shifted slightly forward or backward from that of the typical Otto cycle engine. For example, in the Miller cycle engine, the intake valve may remain open until the beginning of the compression stroke.
While a turbocharger may utilize some energy from the engine exhaust, the series supercharger/turbocharger arrangement does not utilize energy from the turbocharger exhaust. Furthermore, the supercharger requires an additional energy source.
The present invention is directed to overcoming one or more of the problems as set forth above.
According to one exemplary aspect of the invention, a method of operating an internal combustion engine, including at least one cylinder and a piston slidable in the cylinder, is provided. The method may include supplying pressurized air from an intake manifold to an air intake port of a combustion chamber in the cylinder, selectively operating an air intake valve to open the air intake port to allow pressurized air to flow between the combustion chamber and the intake manifold substantially during a majority portion of a compression stroke of the piston, and operably controlling a fuel supply system to inject fuel into the combustion chamber after the intake valve is closed.
According to another exemplary aspect of the invention, a variable compression ratio internal combustion engine may include an engine block defining at least one cylinder, a head connected with the engine block, wherein the head includes an air intake port and an exhaust port, and a piston slidable in each cylinder. A combustion chamber may be defined by the head, the piston, and the cylinder. The engine may include an air intake valve controllably movable to open and close the air intake port, an air supply system including at least one turbocharger fluidly connected to the air intake port, and a fuel supply system operable to controllably inject fuel into the combustion chamber at a selected timing. A variable intake valve closing mechanism may be configured to keep the intake valve open by selective actuation of the variable intake valve closing mechanism.
According to yet another exemplary aspect of the invention, a method of operating an internal combustion engine, including at least one cylinder and a piston slidable in the cylinder, is provided. The method may include imparting rotational movement to a first turbine and a first compressor of a first turbocharger with exhaust air flowing from an exhaust port of the cylinder, and imparting rotational movement to a second turbine and a second compressor of a second turbocharger with exhaust air flowing from an exhaust duct of the first turbocharger. The method may also include compressing air drawn from atmosphere with the second compressor, compressing air received from the second compressor with the first compressor, and supplying pressurized air from the first compressor to an air intake port of a combustion chamber in the cylinder via an intake manifold. The method also includes controllably operating a fuel supply system to inject fuel directly into the combustion chamber, and selectively operating an air intake valve to open the air intake port to allow pressurized air to flow between the combustion chamber and the intake manifold during a portion of a compression stroke of the piston.
According to still another exemplary aspect of the invention, a method of controlling an internal combustion engine having a variable compression ratio is provided. The engine may have a block defining a cylinder, a piston slidable in the cylinder, a head connected with the block, and the piston, the cylinder, and the head defining a combustion chamber. The method may include pressurizing air, supplying the air to an intake manifold, maintaining fluid communication between the combustion chamber and the intake manifold during a portion of an intake stroke and through a predetermined portion of a compression stroke, and supplying a pressurized fuel directly to the combustion chamber during a portion of an combustion stroke.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.